package org.dadacoalition.yedit.preferences.tasktag;

/*******************************************************************************
 *  Copyright (c) 2005, 2008 IBM Corporation and others.
 *  All rights reserved. This program and the accompanying materials
 *  are made available under the terms of the Eclipse Public License v1.0
 *  which accompanies this distribution, and is available at
 *  http://www.eclipse.org/legal/epl-v10.html
 * 
 *  Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
import org.eclipse.core.runtime.Assert;
import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Label;

public class DialogField {

    private Label fLabel;
    protected String fLabelText;
    
    private IDialogFieldListener fDialogFieldListener;
    
    private boolean fEnabled;

    public DialogField() {
        fEnabled= true;
        fLabel= null;
        fLabelText= ""; //$NON-NLS-1$
    }
    
    /**
     * Sets the label of the dialog field.
     */
    public void setLabelText(String labeltext) {
        fLabelText= labeltext;
    }
        
    // ------ change listener
    
    /**
     * Defines the listener for this dialog field.
     */ 
    public final void setDialogFieldListener(IDialogFieldListener listener) {
        fDialogFieldListener= listener;
    }

    /**
     * Programmatical invocation of a dialog field change.
     */     
    public void dialogFieldChanged() {
        if (fDialogFieldListener != null) {
            fDialogFieldListener.dialogFieldChanged(this);
        }
    }   
    
    // ------- focus management
    
    /**
     * Tries to set the focus to the dialog field.
     * Returns <code>true</code> if the dialog field can take focus.
     *  To be reimplemented by dialog field implementors.
     */
    public boolean setFocus() {
        return false;
    }

    /**
     * Posts <code>setFocus</code> to the display event queue.
     */ 
    public void postSetFocusOnDialogField(Display display) {
        if (display != null) {
            display.asyncExec(
                new Runnable() {
                    public void run() {
                        setFocus();
                    }
                }
            );
        }
    }       
    
    // ------- layout helpers
    
    /**
     * Creates all controls of the dialog field and fills it to a composite.
     * The composite is assumed to have <code>MGridLayout</code> as
     * layout.
     * The dialog field will adjust its controls' spans to the number of columns given.
     *  To be reimplemented by dialog field implementors.
     */
    public Control[] doFillIntoGrid(Composite parent, int nColumns) {
        assertEnoughColumns(nColumns);
        
        Label label= getLabelControl(parent);
        label.setLayoutData(gridDataForLabel(nColumns));
        
        return new Control[] { label };
    }
    
    /**
     * Returns the number of columns of the dialog field.
     *  To be reimplemented by dialog field implementors.
     */
    public int getNumberOfControls() {
        return 1;   
    }   
    
    protected static GridData gridDataForLabel(int span) {
        GridData gd= new GridData(GridData.HORIZONTAL_ALIGN_FILL);
        gd.horizontalSpan= span;
        return gd;
    }
    
    // ------- ui creation

    /**
     * Creates or returns the created label widget.
     * @param parent The parent composite or <code>null</code> if the widget has
     * already been created.
     */         
    public Label getLabelControl(Composite parent) {
        if (fLabel == null) {
            assertCompositeNotNull(parent);
            
            fLabel= new Label(parent, SWT.LEFT);
            fLabel.setFont(parent.getFont());
            fLabel.setEnabled(fEnabled);        
            if (fLabelText != null && !"".equals(fLabelText)) { //$NON-NLS-1$
                fLabel.setText(fLabelText);
            } else {
                // XXX: to avoid a 16 pixel wide empty label - revisit
                fLabel.setText("."); //$NON-NLS-1$
                fLabel.setVisible(false);
            }           
        }
        return fLabel;
    }

    /**
     * Creates a spacer control.
     *
     * @param parent The parent composite
     */     
    public static Control createEmptySpace(Composite parent) {
        return createEmptySpace(parent, 1);
    }

    /**
     * Creates a spacer control with the given span.
     * The composite is assumed to have {@link GridLayout} as layout.
     *
     * @param parent The parent composite
     */         
    public static Control createEmptySpace(Composite parent, int span) {
        Label label= new Label(parent, SWT.LEFT);
        GridData gd= new GridData();
        gd.horizontalAlignment= GridData.BEGINNING;
        gd.grabExcessHorizontalSpace= false;
        gd.horizontalSpan= span;
        gd.horizontalIndent= 0;
        gd.widthHint= 0;
        gd.heightHint= 0;
        label.setLayoutData(gd);
        return label;
    }
    
    /**
     * Tests is the control is not <code>null</code> and not disposed.
    */
    protected final boolean isOkToUse(Control control) {
        return (control != null) && !(control.isDisposed());
    }
    
    // --------- enable / disable management
    
    /**
     * Sets the enable state of the dialog field.
     */
    public final void setEnabled(boolean enabled) {
        if (enabled != fEnabled) {
            fEnabled= enabled;
            updateEnableState();
        }
    }
    
    /**
     * Called when the enable state changed.
     * To be extended by dialog field implementors.
     */
    protected void updateEnableState() {
        if (fLabel != null) {
            fLabel.setEnabled(fEnabled);
        }
    }

    /**
     * Gets the enable state of the dialog field.
     */ 
    public final boolean isEnabled() {
        return fEnabled;
    }

    protected final void assertCompositeNotNull(Composite comp) {
        Assert.isNotNull(comp, "uncreated control requested with composite null"); //$NON-NLS-1$
    }
    
    protected final void assertEnoughColumns(int nColumns) {
        Assert.isTrue(nColumns >= getNumberOfControls(), "given number of columns is too small"); //$NON-NLS-1$
    }
    
    

    
}
